The present invention relates generally to devices used to sequentially trim sheet material articles, and in particular to a transfer apparatus for a sheet material article trimmer.
A known apparatus for trimming sheet material articles, such as books, includes a front knife assembly which trims front edge portions of the books and a side knife assembly which trims side edge portions of the books. The front knife assembly includes a front table which moves a book while a front edge portion of a book is being trimmed by a front knife. Similarly, the side knife assembly includes a side table which moves a book clamped to the side table by a pair of clamps as opposite side or head and tail edge portions of the book are trimmed by a pair of side knives.
The known apparatus includes transfer belts which move a partially trimmed book from the front table to the side table and then to the receiving conveyor. The transfer belts are continuously driven at a constant speed. The transfer belts grip a book while it is being moved with the front table. Since the velocity of the front table varies and the transfer belts are driven at a constant speed, the speed of movement of the transfer belts may not precisely match the speed of movement of the book and the front table when the transfer belts grip the book. Book damage and registration problems may result. Similar problems may result if the speed of movement of the transfer belts do not precisely match the speed of movement of the book and the side table when the transfer belts grip the book to move it from the side table. Likewise, problems may result if the speed of movement of the transfer belts do not precisely match the speed of movement of the receiving conveyor when the book is delivered by the transfer belts to the receiving conveyor.
The transfer belts then move the book to the side table. Since the velocity of the side table also varies, the speed of movement of the books by the transfer belts may not exactly match the speed of movement of the side table when side clamps engage a book to hold it against movement relative to the side table. This velocity mismatch can lead to trim quality problems. For example, one side clamp may engage a book before the other due to different thicknesses of the book at the clamping positions. Skewing of the book may result. In addition, due to the changing speed of the side table relative to the constant speed of the transfer belts, there is relative movement between a book and the transfer belts while the book is clamped and is being trimmed on the side table of the known apparatus. This relative movement may damage the book.
The velocity mismatch becomes larger with selective binding due to the difference in thickness in books during a production run.
Such velocity mismatch problems have resulted in side clamps being removed from the known trimmer assembly. When the side clamps are eliminated, the book is gripped by the side knives which trim opposite sides of the book with a straight chop type cutting action. Removal of the side clamps may improve the quality of the trim to some extent, but the level of trim quality has still not been satisfactory due to movement of the book relative to the side table and side knives during the trimming operation.
The above-described known apparatus for trimming books or other sheet material articles is disclosed in U.S. Pat. No. 3,733,947 issued May 22, 1973 and entitled “Book Trimming Machine”. An apparatus for trimming books and other sheet material articles and constructed as disclosed in this patent has been commercially available from Harris Graphics, a division of AM International, of 4900 Webster Street, Dayton, Ohio 45414 and is referred to as the HT-15 Trimmer.